The present invention relates to a laser diode driving apparatus, and more particularly, to a laser diode driving apparatus for driving a laser diode using a write signal having an attenuated waveform.
Recent recording media for information storage utilize high density to store a larger amount of data than existing recording media do. The kinds of recording media are diversified as well. Among the recording media, a mini disk (MD) or a magneto-optical disk (MOD) uses pits which are formed on the disk using laser light emitted from a laser diode, to record data thereon. Furthermore, the data recorded on the disk is reproduced using such a feature that the intensity of the reflected light is varied according to presence or absence of the pits when laser light emitted from the laser diode is reflected from the disk and returned therefrom.
FIG. 1 is a block diagram of a conventional laser diode driving apparatus. FIGS. 2a through 2f are waveform diagrams of input/output signals of the respective elements shown in FIG. 1. In FIG. 1, a mark edge waveform generator 1 receives write data as shown in FIG. 2a and a reference clock of FIG. 2b. The mark edge waveform generator 1 generates a mark edge waveform shown in FIG. 2c by synchronizing the received write data with the reference clock. The mark edge waveform represents a non-return to zero inverted (NRZI) signal in which the level of the waveform is inverted when a zero ("0") or zeros contained in the write data composed of a binary bit stream of "0" and "1" is changed to other value. A write pulse generator 2 receiving such a NRZI signal generates a write pulse train corresponding to pulse widths of the NRZI signal, as shown in FIG. 2d. The write pulse train is represented as waveform corresponding to a period 2T through 8T of the NRZI signal, in which T corresponds to a period of the reference clock. The write pulse generator 2 supplies the write pulse train to a laser diode driver 3. The laser diode driver 3 makes current flow through a laser diode 4 according to the write pulse train. As a result, a write domain is formed on the disk as shown in FIG. 2e. FIG. 2f is a waveform diagram of a reproduced signal detected from the data recorded on the disk using the laser diode 4.
As described above, a conventional laser diode has been driven using a write pulse train whose T/2 pulse repeats according to pulse widths of the NRZI signal. However, since a pulse width becomes narrow in a disk on which data is recorded at high density, it is not so easy to accurately produce a T/2 pulse. Considering a response time of currently commercialized devices, the structure of a laser diode driving device becomes complicated to accurately produce a T/2 pulse. In addition, the cost of the set increases. Furthermore, since a reproduced signal includes jitter in a high density disk, signal distortion and time-base swing occurs, and a carrier-to-noise ratio is lowered.